1. Field of the Invention
The present invention relates to an image forming apparatus, a control method therefor, and a computer-readable storage medium storing a program for implementing the method.
2. Description of the Related Art
Conventionally, there have been image forming apparatuses having a sheet holding unit such as a manual feed tray. The manual feed tray has a guide for measuring widths of sheets. The width of the guide can be set to the same width as a main scanning width or a sub scanning width of a regular size such as A4 or B4, and when the guide is set to this width, a regular size corresponding to this width is set as a size of a sheet for use in printing.
In relation to this, a technique to reset a size of a sheet for use in printing when a difference between the size of the sheet and an already-registered size of a sheet is equal to or greater than a threshold value based on measured values of a guide width, a length, and so on (see, for example, Japanese Laid-Open Patent Publication (Kokai) No. 2004-352440).
According to Japanese Laid-Open Patent Publication (Kokai) No. 2004-352440, however, when an image is to be formed using an irregular-size sheet, information obtained from the guide cannot be effectively used. For example, when a user would like to form an image using an irregular-size sheet having a slightly shorter main scanning width than a width of an A4-size sheet in a main scanning direction, he or she places the sheet on a manual feed tray and brings the guide closer to the sheet until the guide abuts on an end of the sheet.
Because the width of the guide is set to a width other than a width of a regular-size sheet, an image forming apparatus cannot recognize the width of the sheet and thus displays a setting screen to make the user select a sheet again. Alternatively, the image forming apparatus notifies the user that the width of the guide is not set to a width of a regular-size sheet, and then terminates the process.
Thus, whenever the user places an irregular-size sheet on the manual feed tray, he or she needs to input the size of the placed sheet using an operation panel.
In recent years, the number of irregular-size sheets has been increasing, and hence users need to select a sheet for use in image formation from among a large number of irregular-size sheets.